Latest Sun Flare Put at X28, Strongest on Record

Update, 7:20 A.M. ET,
06 November 2003:NOAA's Space Environment Center (SEC) has classified
this flare as an X28, making it in fact the strongest ever recorded. A source
told SPACE.com that the SEC is aware other scientists still think the
flare was even stronger. The article below remains as it originally appeared. -
RRB

A flare released by the
Sun on Tuesday could be the most powerful ever witnessed, a monster X-ray
eruption twice as strong as anything detected since satellites were capable of
spotting them starting in the mid-1970s

The strongest flares on record, in 1989 and 2001, were rated at X20. This one
is at least that powerful, scientists say. But because it saturated the X-ray
detector aboard NOAA's GOES satellite that monitors the Sun, a full analysis has
not been done.

The satellite was blinded for 11 minutes.

Craig DeForest, a solar physicist at the Southwest Research Institute, said
others in his field are discussing the possibility that Tuesday's flare was an
X40.

"I'd take a stand and say it appears to be about X40 based on
extrapolation of the X-ray flux into the saturated period," DeForest told SPACE.com.

That estimate may even be conservative, he said.

The flare leapt from a sunspot that is rotating off the visible face of the
Sun, so its effects were not directed squarely at Earth. Nonetheless, a radio
blackout occurred at many wavelengths as the storm's initial radiation arrived
just minutes after the eruption. Radio blackouts are ranked from R1 to R5 by
NOAA's Space Environment Center, the space counterpart to the National Weather
Service.

"This is an R-5 extreme event," said SEC forecaster Bill Murtagh.
"They don't get much bigger than this."

Paal Brekke, deputy project scientist for the SOHO spacecraft, which monitors
the Sun, also told SPACE.com the outburst could be as strong as X20
"or much higher."

At least X20

The SEC is still evaluating the flare's ranking.
For now, they are calling it an X20+, indicating that it is indeed the most
powerful on record. The only known event that might outrank it is an 1859
solar storm that zapped telegraph lines
in an era when solar monitoring could not provide an evaluation of a flare's
strength.

The radiation flare was accompanied by a coronal mass ejection (CME), an
expanding cloud of charged particles -- actual matter that moves at supersonic
speeds but not as fast as light. Had this CME been aimed at Earth, scientists
would have feared a potential space storm unlike anything seen in the Space Age.

As it is, the expanding cloud is expected to provide a glancing blow sometime
Thursday.

The storm, if it arrives, will not likely be major, forecasters say. But as
with all space weather, satellites and communication systems will be at risk of
disruption or damage. Colorful sky lights called auroras may be active at high
latitudes and possibly into northern U.S. states and Europe.

More to come?

Tuesday's flare was generated by Sunspot 486, which is about 15 times the
size of Earth.

Sunspots are dark, cooler regions of the solar surface, areas of pent-up
magnetic activity. They're a bit like caps on a shaken soda bottle, and
upwelling matter and energy can blow at any moment. Scientists cannot predict
when a flare will occur.

During the past two weeks, number 486 and two other large sunspots set off
nine other major flares. It was one of the stormiest periods of activity ever
witnessed, all experts agree. The number of intense flares, some shooting out
within a day of another, was unprecedented. Auroras were seen as far south as
Texas and Florida.

The second strongest flare in this historic two-week series was an X17 event
on Oct. 28. It was aimed at Earth and generated severe geomagnetic storming when
it blew past the planet less than 24 hours later.

A period of relative calm is now expected on the solar surface. But another
round is possible.

The Sun spins once on its axis once every 25 days at its equator, carrying
sunspots around. Sunspots can last days or weeks. Any of the three that have
rotated off the right side of the Sun could return in about two weeks on the
left side and, possibly, send more major storms toward Earth.